Generation control system



Jan. 1, 1963 F. B. DAvls 3RD GENERATION CONTROL SYSTEM Filed may s, 19614 Sheets-Sheet 1 @hul hill..

Jan. l, 1963 F. B. Avlsv 3RD GENERATION CONTROL SYSTEM 4 Sheets-Sheet 2Filed May 3. 1961 ...ozemcmm l urwwo l .522m

i' :t Area Requirement Jan. l, 1.963 F. B. DAvls 3RD GENERATION CONTROLSYSTEM Filed May 3, 1961 y 4 Sheets-Sheet 3 Jan. 1, 1963 F. B. DAVIS 3RDGENERATION CONTROL sYsTEM 4 Sheets-Sheet 4 Filed Nay s, 1961 JIOI Lno

United States Patent Oiiice V3,071,6aa Patented Jan. l, 1963 Filed Mays, 1961, ser. No.`1o7,ss1 1s claims. (c1. 301-53) This invention relatesto control of the generation of power for an interconnected area made upof'a plurality of generating stations and has for an object theprovision cfa function genera-tor for producing outputs respectivelyrepresentative of desired generation of each station in accordance withselected corresponding portions of the several loading curves of thegenerating stations.

In accordance with the present invention, advantage is taken of the factthat the loading curves for the respective generating stations may beapproximated by a plurality of straight-line segments, some of whichhave slopes differing from the others. The several loading curves havebreakpoints (where a straight-line segment meets a second straight-linesegment) which occur at selected and corresponding values of the totalgeneration requirements of the generating area. By providing means forgenerating a plurality of signals, each corresponding respectively inmagnitude with the desired values of generation of each station atcorresponding breakpoints, together with an additional means forgenerating a signal representative of the generation requirements of thearea, there may be obtained from a computer jointly responsive to theaforesaid signals outputs representative of the generation needed tomeet the total requirements of the area and yet respectivelyrepresentative of the desired generation of each said stationl asdetermined by the individual straight-line segments between adjacent'breakpoints Further in accordance with the invention, there areprovided means responsive to the total controlled-generationrequirements of the interconnected area for establishing operation ofthe computing means first in accordance with the individu-alstraight-line segments between a first pair of adjacent breakpoints andthen between a different adjacent pair of breakpoints and as required bythe magnitude of the total generation requirements. By reason of theforegoing provisions, each of the plurality of output signals isrepresentative of the desired generation of a station which stationstogether meet the total generation requirements of the area. This meansthat in terms of the operation of the system as a whole, operators haveat hand outputs which, as appearing on instruments or as applied tocontrol systems, may be calibrated in terms of generation, thusproviding a simple, reliable sys'- tem with minimum demand on the partof the operator to achieve optimized operation of the several'generating stations. For a more comprehensive understanding of thepresent invention together with its underlying theory and for furtherobjects and advantages, reference is to be had to the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 diagrammatically illustrates a simplified embodiment of theinvention;

Z been illustrated as adjacent each other and suii'iciently close that asingle conductor 27 may have applied thereto outputs from potentiometers25 and 26. In practice, it will be understood that the stations will bewidely separated and that the ycomputing system later to be describedmay be located at 'the load dispatchers oiiice which may or may notcoincide with the location of a station, y The -telemetering connectionsbetween stations and the load dispatchers otlce are well understood bythose skilled in Vthe art and include means for reproducing at the vload dispatchers oiiice the outputs from the potentiom- FIG. 2illustrates graphs helpful in explaining the ineters, together withmeans for sending to the stations signals for producing desiredgeneration by the stations.

y.These generators 10 and 11 are respectively connected throughwattmeters 12 and 13 to a transmission line 14 which, in turn, isconnected to a tieline 15 which, through a wattmeter 16, extends to theother areas likewise including a plurality of interconnected generatingstations. As well understood by those skilled in the ar-t, each stationwill include one or more generators, and the station characteristiccurve representing ythe proportion of the total area-generationrequirements to be shared by a station may be represented by a Vcurveapproximated by a plurality of interconnected straight lines.

For example, in FIG. 2 the loading curves 20 and 21 for the Stations Aand B include initial segments 20a, 21a, intermediate segments 20h, 21b,and ii'nal segments 20c and 21C. The segments 20a-20c and 21a-21C havecorresponding breakpoints at X1, X2 and X3, i.e., where the adjacentstraight-line segments meet. These breakpoints at X1, X2 and X3 occur atthe same values of the total system generation on control plus or minusthe area require-V ment of the generating area. Thus, the curves havebeen plotted with total generation requirements of the generating areaas abscissae and with Station-desired-generation as ordinates. The curve22 and 23 are similar and are exemplary of the loading curves foraddiional stations of which there may be many in the generating area. Ifthe generation requirements of the area lie between X1 and X2, then forthe Stations A and kB the loading should be as indicated by the segments20h and 2lb, each of which represents a linear relationship betweenstation loading and total generation requirements. l

It is to be understood that the loading curves 20-23 will represent theoptimum loading of eaehstation, taking into consideration the generatingfacilities available, theirl relative capacities and the applicableincrement-al costs These curves may include the weighing of such factorsas loadings and losses on transmission lines within vthe areas, thestream flow and storage conditions of hydroelectric plants, and theloading curves. The loading curves may be those produced by computers ofkinds well known to those skilled in the art, including those of theanalog and digital type and also loading slide rules which correlate forcomputation purposes a plurality of conditions.

A feature of the present invention resides in the fact that when thetotal generation requirement lies between X1 and X2, the curves `2Gb and2lb will be set into a computing network by setting therein the valuesof the ordinates for the respective breakpoints 20d, 20e and 21d, 21e.The values for the abscissae corresponding with X1 and X2 are obtainedby summing operations laterl to be explained.

Returning now to FIG. 1, genenation-representative signals are derivedfrom slidewires 25 and 26, the movable contacts 25a and 26a of which arerespectively adjusted by the Wattrn-eters 12 and 13 for application t-oan input conductor 27 of a summing amplifier 28.` The circuits from thecontacts 25a and 26a respectively include summing resistors 31 and 32.The input conductor 27 also 4has applied to it by way of a summingAresistor 33` an error signal commonly referred to as area requiremenThis area-control error-signal is obtained from a slidevv-ire 34, themovable contact 34a of which is adjusted in response to change infrequency of the system and the flow of power to and from the area undercontrol -by way of` tieline 15. Thus, the contact 34a is aidjusted inaccordance with a control system 36 which produces a mechanical outputproportional to the magnitude ofthe area requirement as determined Vfromthe outputs from a frequencymeter 37 andthe wattmeter 16. Such an arearequirement system is ldisclosed in Carolus Patent 2,688,728.

From the foregoing, it will be seen that the input to the 'amplifier' 28represents the sum of the actual generation of the several stationsincluding generators and 11 and the area requirement. The kactualgeneration will hereinafter frequently be referred to as the controlledgenerationin that provisions will later be described by means of which astation, after reaching a predetermined limit, 'will no longer besubject to change in generation and, accondingly, that station will beremoved from the summing circuit just described.

`The amplifier 28 produces on its output circuit an outputrepresentativeof the total generation requirements of the system as a whole. Thatoutput is applied by way of a negative feedback resistor 38 to the inputcircuit to provide the heretofore described summing action. The signal`representative of the total generation requirements of the system isapplied by way of a summing resistor 41 to asumming amplifier 42 whichalso receives at its input circuit through summing and feedbackresistors 43 and 44 signals representative respectively of the desiredgeneration for Stations A and B. krIhe signals applied by Wayof theresistors 43 and 44 are negative as compared with the signal fromresistor 41 and, therefore, reduce thelinputfsignal to the summingamplier 42 to aflow value, approaching zero as a limit.

The -output of the amplifier 42 has been indicated to be -`E0. Thatoutput is applied to an input resistor 45 of an inverter 46, shown as anamplifier, with a negative feedback circuit including a feedbackresistor 47. The inverter 46 produces an output which has been labeled+En. The outputs from the amplifiers 42 and 46 are applied to lineslabeled respectively -i-Eo and -E0. To the former there are connectedvoltage dividers shown as lpotentiometers 51 and 52, Whilepotentiometers S3 and 54 are connectedto the ylatter line. The movablecontacts of these potentiometers have Ibeen labeled Yal,

Yaz, Ybl and Yb2. An additional potentiometer 55 with its movablecontact labeled Yal is preferably identical with potentiometer 51,though supplied from a constant voltage source marked S. (Otherpotentiometers in the system, where supplied from Ya separate source,have similarly been illustrated with input terminals to which there hasbeen applied the reference character S to indicate a suitable source ofsupply. The system may function either with direct current oralternating current, this being the reason for the adoption ofthe symbolS.)

`As will be later explained, the breakpoint d is set on potentiometer 51by the contact Yal, which contact has associated with it `a scalecalibrated in terms of station generation. Similarly, the breakpoint 20ewill be set'by the'contact Yag, and the -breakpoints 21d and 21e will beset in their respective potentiometers by the contacts Ybl and Yb2. Itwill be observed that the contacts Yal and Y'al are mechanicallyinterconnected as by the connection illustrated by the broken line 56 sothat the contact Ya1 has a setting corresponding with that of Yal. fWith the-foregoing setting of the ordinate contacts of potentiometers51-55, the generation of Stations A and B will be regulated inaccordance with the straight-line sections 2Gb and 2lb of the loadingcurves of FIG. 2. This result is,` accomplished in part by theconnections of the'contacts Yal, Yal and Ya2 to a summing amplifier 58"V by way of summing resistors 59 and 60 and 61. The summing amplifier5,8` is provided with a negative feedback resistor 62. The output fromthe summing amplifier 58 is applied to output terminals `63, the outputsignal being representative of thedesired generation of Station A forthe existing total generation requirement of the area. The output signalfrom the amplifier 58 is likewise applied by way of a conductor 64 tothe negative feedback resistor 43. As later explained, there will beprovided Vfor Station B an additional y.amplifier corresponding with theamplifier 58 for producing an output signal corresponding with desiredgeneration for Station B, and the output therefrom will be applied byway of a conductor 65 to the negative feedback resistor 44 forming apart of the computer'for determining desired generation for Station A.

It will be obvious from an inspection of the input circuit to thesumming amplifier 5S thatthe output will be proportional t-o the severalinputs.k Accordingly, instead of utilizing the single feedback circuitfrom the output Station A-Desired Generation L-Einf Y'ai-l- Y'biil( Yaz-Yal) (Yazl Ybz) f Yat-l Ybi) The foregoing equation states that StationA desired generation is explicitly determined in terms of the setting ofthe contacts on potentiometers 51-55 and by an input signal Em, if thissignal -Em ber taken as representativeY of the total desired generationand of a value lying between the limits X1 and X2. From FIG. 2 itwillvbe seen that the total systm generation on control, plus or minusthe area requirement for the point X1 is equal toV Yal-i-Ybl. Similarly,the system generation for the point X2 is equal to Yaz-i-Ybg. Theforegoing assumes'the stations represented by curves 2,2 and 23 are notunder control, having reached a control limit. y

If itnow-be assumed that the total system generation on` control, plusor minus the area requirement, has a valueof Em, then the value betweenX1 and Em'will be equal. to (E1n-X1) which is equal to [Em-(Yal-l-Ybl.If this quantity be multiplied by the ratio of ythe distance (yal-H12)to the distance (X 1-X2) and there be added to the product thevalue ofYal, there will be determined Ya, the desired station generation. Thedistance (Ya2-Ya1) has a value represented by the settings of thepotentiometers'Sl and 53. The distance (X1-X2) may likewise bedetermined by a summation of the'values representative of the ordinatepoints previously identified.

The foregoing may be summarized mathematically. The output from thesumming amplifier 58 as it appear at output terminals 63 may beexpressed as follows:

The first term on the right-hand side ofv Equation 2 sets forth that theinput signal applied to the summing resistor 61 is equal to the productof -E0Ya2 divided by the total resistance, Yt, of the resistor orpotentiometer .53.. This term as it appears in the output of amplifierS8 lis inverted, i.e., its sign changes to a plus. Similarly, the secondterm represents the ratio of the product -l-EoYal and the total,resistance Y1, of Ithe resistor A51, ythesign again reversing as thesecond term appears at the output. of amplifier 58. The third term isderived from the resistor or potentiometer 55 and has a value of fYl.;as applied to resistor-60,

For convenience, that equation is as It will be obvious that there willbe a corresponding equation for Station B, and it is as follows:

EB=E1O7=EW2 YtWl+1/'a 4) Considering now the summing amplifier 42 andremembering that the resistors 43 and 44 are negative feedbackresistors, 'the effect will be to reduce the input to the amplifier 42to a small value, approaching zero as a limit. (The amplifier 42 has ahigh gain so that zero may be approached to a close approximationwith'the amplifier 42 still having a finite output for producing theoutput corresponding with -E`.) v

Applying Kirchhoffs law and considering the input to the amplifier 42 asa current-junction point, then all of the currents entering and leavingthat point will be equal to zero. Considering that the resistors 41, 43and 44 are all equal to unity, and that the current to the amplifier 42is substantially zero, then the following equation applies:

i Equation 6 may now be substituted in Equation 3 to obtain thefollowing:

It wilLbe recognized that the right-hand expression of Equation 7 is thesame as Equation l as it appears in FIG. l, thus establishing themathematical accuracy of that equation. It is here emphasized that Em,representative of the total desired system generation at a given pointlying between the established limits must be introduced into the systemas a negative quantity to satisfy Equations l and 7. Explicitly, Ein,the voltage applied to theinput vof the summing resistor 41, is negativewith respect to the Voltage applied to the output of that summingresistor as from the negative feedback resistors 43 and 44. Ein willhave the same polarity or phase as the source S supplying the resistorS.

It is to be here observed that the value of Ya1 is equal to the value ofYal, that is to say, these two terms both identify the same ordinatevalues for the breakpoint d. Similarly, Ybl and Y'b1 represent the sameordinate values for the breakpoint 21d.

In the foregoing, the simplest form of equation has been utilized,though in FIG. 2 there have been illustrated the additional loadingcurves 22 and 23 which may, of course, be taken into account by a simpleexpansion of the system as clearly indicated -by the foregoingdevelopment.

There will now be considered the operation of .the system in which thetotal desired system generation moves from a range between the values X1and X2 to the values X2 and X3. Such a system has been illustrated inFIGS. 3A and 3BY where corresponding parts have been given correspondingreference characters.

In FIGS. 3A and 3B it will be observed that the output circuits frompotentiometers 25 and 26 include single-pole, double-throw switches '71and 72. These are provided in order to remove from the input circuit ofa summing amplifier 28A the signal representative of station generationat any time the generation of that station reaches a limit. Whenever astation reaches one of its limits and its corresponding double-throwswitch (71 or 72) is operated as just described, its correspondinglimit-setting means will at that time be operated on its slidewire toits zero position. This may be done either manually, or by providingsimple relay means (not shown) which upon opening of one of the switchesdeenergizes the voltage divider or slidewire comprising suchlimit-setting means. The summing amplier 28A functions in a mannersimilar to the amplifier 28 of FIG. 1 but differs in that it has appliedto its input circuit signals representative of the generation of StationA and of Station B without having applied to its input circuit signalsrepresentative of area requirement.

In the system of FIGS. 31A-3B, the area requirement signal from theslidewire 34 is applied by way of a summing amplifier 42 which alsoincludes a summing resistor 41 connected to the output of amplifier 28A.Though not necessarily essential to the invention, the above arrangementhas been illustrated to have developed on conductor -73 a signalrepresentative only of actual controlled generation of the area and withthe area requirement divorced therefrom. Though the relays may beoperated from a combined signal, in the arrangement shown there will beutilizedva slower changing signal in conjunction with the operation ofrelays later to be described.

Potentiometers corresponding with potentiometers 51- 55 of FIG. l are inFIGS. 3A-3B identified by the reference characters Ya1-Ya4, Y'a1-Ya4,etc., and respectively applied to the movable contacts thereof. Thevoltage dividers or potentiometers for values Yb1 etc. are energizedfrom source S by way ofy conductor 134 and the grounded conductor G.These potentiometers correspond with four-segment loading curves, onlythree of which have been shown in FIG. 2. In the system of FIGS. 3A-3B,there are automatically determined the linear segments of the loadingcurves along which there will be controlled the generation of thestations, and in response to the foregoing summation circuits there willbe set into the computer the corresponding ordinate values of thebreakpoints of the loading curves. Assuming the parts are in theirillustrated positions and that the total system generation on controlhas the value Em as illustrated in FIG. 2, the following occurs.

There are applied to the input circuit of a summing amplifier 74 of thenegative feedback type, by way of conductors 81 and 82, signalsrepresentative of the ordinate values corresponding with Yal and Ybl,the sum of which for a two-station system is equal to the value X1 ofFIG. 2. If the sum of the actual generations from all stations begreater than the sum represented by the ordinate points Ya, and Ybl, itwill be known that these two stations will be loaded in a region abovethe abscissae value X1 of FIG. 2. The foregoing comparison is made byapplying the output from amplifier 74 through a summing resistor 83 toan amplifier 77 which also has applied to its input the signal ofconductor 73 as by way of summing resistor 84. Assuming that the sum ofactual generation exceeds -in magnitude the sum of the ordinate values,then the amplifier 77 will have an output for energization of theoperating coil of a relayv 85 which closes its normally open contacts.Similarly, the amplifiersV 75 and 76 have respectively applied theretoas by conductors 86, 87 and 88, 89 input signals respectivelyrepresentative of the ordinate points Yaz, Ybz and Ya3, Ybg. Similarly,amplifiers 78 and 79 compare respectively rthe magnitudes of the outputsfrom amplifiers 75 and 76 with the actual generation signal of conductor73.

It will be remembered that the energization of relay 85 represented onlythe fact that actual generation exceeded rthe sum of the initialordinate points. If now the output 4of amplifier 78 energizes the coilof a relay 90, it will be known that the actual generation exceeds thesum of the ordinate points at the point X2 of FIG. 2. In such an event,the normally closed contacts 90a of relay 90 are opened Ito eliminatethe effect of the contacts 85a on control system features later to bedescribed. Similarly, if the amplifier 79 energizes the operating coilof relay .91, it will be known that actual generation lies above thepoint X3 of FIG. 2. However, if only thev relay 85 be energized, it'Willbe knownthalt actual generation corresponds with a value such'as En, ofFIG. 2 and in the range betweenX1 and X2.

The. closure of contacts 85a of` the relay 85 completes an energizingcircuit for the operating coil of a relay 95 which thereupon operates toclose ,its normally open, upper` contacts, thereby to connect the outputvoltage (.-E) from summing amplifier 42 to the conductor 96. It may behere observed that in the deenergized position of relay 95, the outputvoltage of amplifier 42 is connected to the conductor 97. In thedeenergized position of relay` 95, conductor 96 is connected through thelowermost, normally closed contacts to the output voltage (7l-E0) fromthe .inverter 46. Similarly, in fthe energized position of relay 95conductor 97 is` connected to the output of the inverter 46. Thus therelay 95 is a circuit reversing means which reverses the relativepolarities of conductors 96 and 97 relative to ground conductor G, andfor purposes later to be described. With the relay `95 energized,conductor 97 is connected to the voltage -i-Eo, and the conductor 96 tothe voltage E0 which conforms with the system of FIG. l where thepotentiometers of contacts Yal and Ybl were connected to +En, while the:potentiometers for contacts Yaz and Ybg were connected tothe voltage-E0.

The closure of-contacts 85h of relay 85 completes an energizing circuitthrough Ithe normally closed contact` 91h for the operating coil of arelay 98 which thereupon closes its contacts to connect the contact Yazto the summing resistor 61 of amplifier 58. There is completed by thenormally closed contacts 90b of relay 90 an energizing circuit forarelay 99 which is thereby operated to close its contacts to complete aconnection from contact Yal to the summing resistor 59.r

The relay contacts 90b and 911: also complete energizing circuits by wayof conductors 100- and 101 for relays t 102 and 103, which thereuponclose to complete circuits from contacts Ybl and Ybz to the summingresistors 104 and 105 of the negative feedback type of summingarnplifier 106. rl`he output of the amplifier 106 develops at outputterminals 107 a signal E107 representative of the desired generation forStation B. As explained in connection with FIG. 1, that output signal isapplied by way of Iconductor 65 to the summing resistor 44 of amplifier42 and is so illustrated in FIGS. 3A and 3B. For convenience, the outputterminals 63 have again been illustrated in FIG. 3B, and they haveapplied thereto by way of conductor 64a a signal E63 representative ofthe desired generation for Station A.

The closure of contacts 85h of relay 85 also completes an energizingcircuit by way of normally closed contacts 90C of relay 90, normallyclosed contacts 91e` of relay 91, fora relay 108 which cl-oses itscontacts to complete a circuit from the contact Yal by Way of summingresistor 60 and conductor 109 to the input circuit of the summingamplifier 58.

The closure of contacts 85h also completes by way of a..conductor 110 anenergizing circuit for a relay 111 which is vthereupon energized tocomplete a connection from Ithe contact Ybl through a summing resistor112 to the input conductor 113 of the summing amplifier 106.

There have now been established in the system of FIGS. 3A and 3B thecircuits above described for FIG. 1. Accordingly, a description of theoperation of the system of FIGS. 3A and 3B need not be repeated.

Assuming .now that the total controlled generation as represented by thevoltageon conductor 73 exceeds a value corresponding with X2 of FIG. 2,and thus exceeds inmagnitude the output from amplifier 75, the amplifier78 will energize the relay 90 which thereupon operates to close itsnormally open contacts 90d and to open its contacts 90er-90e. It is ,tobe noted the relay 85 remains energized. The opening of the relaycontacts 90a deenergizes the relay 95 which thereupon Vreturns to itsillustrated position to connect-the outputof amplifier 42 to,

'the conductor 97 and to `connect the inverter 46 tio-the conductor 96.This operation has the effect of changing the breakpoint Xztwhichpreviously represented .the upper limit to a breakpoint correspondingwith the lower limit of the range between X2 and X3. The openingiofcontacts b, of course, deenergizes relays 99 and 102, Simi-A larly, ftheopening of contacts 90C deenergizes relays 108 and 111.

The closure of relay contacts 90d energizes a relay 114 and by aconductor 115 energizes a relay 1116. The relay 114 connects the contactYa3 to a summing resistor 117 i of amplifier 58, while the relay 116connects the contactt Ybg to a summing resistor 118` of the amplifier106.l There are also completed by way of contacts 90d ener.

gizing circuits for relays 119 and 120. Both circuits may be traced byWay of normally closedcontacts` 91d Vofi relay 91. The second energizingcircuit isfcompleted by way of a conductor 121; The relays 119andf120-complete circuits respectively from the contact-Y-'az byway of asumming resistor 122 to the conductor 109 of Tam` plifier 58; and fromthe contact Ybz by way-of a sum-w ming resistor 123 to the conductor 113of summing `amplifier 106.

There have now been established the connections for operation of thesystem in the sa-me mannernas described` functions may now be expressedas ,follows For Station A:

l Ee3:[ E1n (LZ-I Y b2)](Ya/3 }a2) Y/a?A not been illustrated in FIG. 2,it will be understood that in practical applications there may be manysuch additional segments, and thus the terms of the applicable equationswill take into account these additional segmentsas Well as an increasednumber of stations.

If there are n stations and m represents the lowerj breakpoint of theapplicable load-curve segment. Y=Desired Sta. Glen.=[-.Eia-(Yam-l-Pbm-lr. Ynm)](Yn m+D.-Ynm) t (10) When the total systemgeneration on controlexceedsd the value of X3 of FIG. 2, then theamplifier 79vWill energize the relay 91 which, upon closing its contacts91a,` energizes the relay 95, and onV opening its contacts 91`b,1l t 91Cand 91d deenergizes relays 98, 103, 108,111, 119.! and 120. The closingof its contacts 91e energizes a relay s 124 to connect contact Ya., byway of summingrresistor 125 to the amplifier 58. There is also energizeda relay 126 which connects contact Ya3 by way of 'summing-resistor y127to input conductor 109ot'amplifier 58, and y contacts 91e of relay 91also complete by way of-conductors 128 and 129 energizing circuits forrelays 130 and 1311; The relay 130connects contact Yb4 by way of asumming resistor 132 to'the amplifier 106, while the relay 131' fconnects the contact Yb3 by way of a summing resistor` 1,33 to inputconductor 113 of amplifier 106; Accord-f` ingly, the system nowfunctions to produce outputsat output-terminals 63 and 107representative of the desired7 generation for Stations A and B withV theoperationbe- Vtween the limit X3 .of FIG;Y 2 and the l-imit X4 V(notshown in No.2).

- In practice, there will be additional stations, and these Willl beprovided for by providing duplicatesof that part of the systemillustrated in FIG. 3B, one for each station. The simple extension of`the system to include additional stations will be quite obvious fromvthe manner in which. there has been added to the system of FIG. 3A thefeatures which include Station B asa part thereof.

Now that thev invention has been explained in connection with typicalembodiments thereof, it will be understood `that many modifications maybe made within the scope of the appended claims. t

In summary, the invention includes ananalog computing network having aplurality of adjustable circuit elements Yel, Ybl, etc., corresponding`in number with the number of breakpoints of the loading curves andrespectively adjustable to values proportional to the several levels ofstation generation at the breakpoints. Selected circuit components areby the relays previously described connected to the input conductor ofthe summing amplifier 58 with one of the circuit components representingthe gener-ation level at the lower limit of a linear segment of aloading curve. By providing additional amplifying means, such as theamplifier 42, selected circuit components are energized from the outputof that amplifier with other circuit elements energized from an inverter46, all as has been described in connection with the conductors 96 and97 and the circuit-reversing means 95. The foregoing circuit componentsand corresponding with Ya1, Ybl, etc., provide means for establishingthe limit signals as from the outputs of summing amplifiers 74-76 foractuation of the comparison amplifiers 77-79 to predetermine the circuitcomponents connected to the summing amplifier S8. The system iscompleted by the feedback connection to the input conductor of summingamplifier 4Z, these feedback connections applying thereto the desiredstation generation for the several stations under control.

Though the present invention has been explained in considerable detailYin connection with generation control systems, it is to be understood itis not liimted thereto, since the control features thereof areapplicable to widely differing systems. The invention is particularlyadapted to the control of generation of sources whether of a pluralityVof interconnected generators including tielines, the generatorsconsidered in groups as in stations, or as combined by la plurality ofstations fo form areas or as areas controlled as described above for theStations A and B.

As described above, the signal appearing on conductor 73 representsactual controlled generation. signal on conductor 73 is to include arearequirement, then an additional summing resistor will be addedy to eachof the inputs of amplifiers 77, 78 and 79, and to each said summingresistor there will be applied the signal from the slidewire 34 which isproportional to area requirement.

4It will be added algebraically to the signal on conductor 73, that isto say, it may be either subtractive or additive. Accordingly, thesignal effectively applied to amplifiers 77-.79 as vfrom conductor 73-as well as the signal fromV breakpoint of the applicablesegment Wherethe e What is claimed is: l. A system for dividing an input signal intoa plurality of output signals the sum of which is representativev ofsaid 4input signal comprising means for, establishing for each outputsignal an upper and lower limit of its range over which said outputvaries in linear relation with said input, means for summing saidestablishedlimits for each said output for producing the correspondingupper and lower limi-ts of the range for said input signal, an outputsumming means, and means for applying to said output summing means foreach said output quantities representative of 4the lower limit of therange for its respective output and representative of the amount .saidoutput should be above said lower limit in accordance with the amountsaid .input is above the lower limit of said cor- Aresponding inputrange for producing from said output summing means said output signals.

2. A system' as' in claim l and including an input sumi ming means towhich is applied said input signal and said output signals whereby thesum of said output signals is at all times proportional to said inputsignal.

3. In a generation control system having means for producing an inputsignal of amplitude representative of a total desired generation, Ithecombination of means for dividing said input signal into a plurality ofoutput signals each representative of the desired generation of a sourcecomprising means for establishing for each said output signal an upperlimit and -a lower limit between which each said output signal varies asa linear function with change in said input signal, summing meansresponsive respectively to signals representative of said upper and saidlower limits for producing corresponding upper and lower limi-ts of saidinput signal, output summing means, `and means for applying to saidoutput summing means quantities representative of said lower limits ofeach said output signal and representative ofthe amount each said outputsignal should betaboveits lower limit in proportion to the `amount saidinput is above its said lower limit for producing from said outputsignals outputs each representative of the desired generation for saidsources. y

4. The combination of claim 3 in which there are provided meansresponsive to said input signal and to said summing' means for saidlimits for concurrently changing the respective ranges between saidupper limits and said lower limits lof said output signals to establisha new range over which each said output signal varies in linearrelationship. f

5. The combination of claim 4 in which said last-named means establishesfor the new range lower limits corresponding with the upper limits ofthe range previously established or in which the lower limit of therange previously established corresponds with the upper limit of the newrange.

6. The combination of claim 5 in which there are provided a plurality ofcircuit-controlling means for establishing the control range betweenselected upper and lower limits for said source in response to themagnitudes of said input signal and of the output of saidsumming meansfor said limits. v

7. In a generation control system for a plurality of sources and inwhich each 'source has between a lower limit and an upper limit a linearrelationship between its change of generation and change in totalgeneration, cornprising means for generating signals Yal and Ya2representative respectively of said lower and upper limits of saidsource generation, means for generating signals X1 tively equal to meansfor generating a signal (V-EBJ representative of the total desi-redgeneration and lyingl between said upper and-lower limits Vfor saidtotal generation, and means for producing -an outputsignal of magnitudeproportional to the signal Yal plus-the product ofthe diierence betweenthe signal Emminus the signal `X1 multipliedby the difference betweenthe signal Yaz and Ya; yand divided by the diierence `between the signallX2 minus X1 Vfor determining the desired generation of a `source whereX1 represents the sumy of said signals corresponding with the lowerlimits of 'each range of leach source and where Xzequals the -sum of thesignals representative of said upper limit of said range lof each sourcewhereby there is produced an operation pursuant to the followingequation where the desired generation of a source equals 8. 'A functiongenerator for an interconnected generatingarea made up of a plurality ofgenerating stations each having at least one generator, each of saidAgenerating stations .having a loading curve representing the desiredgener-ation of the station in terms of the total controlled-generationrequirements of thearea and approxi- .mated by a plurality-ofstraight-line segments some of which have slopes differing from others,each said segment joining an adjacent segment at a breakpoint, thecorresponding breakpoints ofall of said loading curves occurring atcorresponding values of said total controlledgeneration requirements ofsaid area, comprising means for` generatingv aplurality of signals eachin magnitude proportional to desired valuesof generation of veachstation at corresponding breakpoints, means `for generating a signalrepresentative of said controlled-generation lrequirements'of-the area,computing means jointly responsive to said-signals for producing outputsto meet said total controlled-generation'requirements of said area andrespectively /representative of desired generation of each said station,andmeans responsive to said requirements of-the area for establishingoperation of said computing means in accordance with the corresponding4individual straightlin'e vsegments determined by adjacent breakpoints.

9. A function generator for an interconnected generatingarea made up ofa plurality of generating stations each' having at least one generator,each of said generating 'stations having a loading curve representingthe desired generation ofv the station in terms of the totalcontrolledgeneration requirements of the area and approximated by aplurality of straight-line segments some of which have slopes diiering'from others, each said segment joining anf'adjacent segment at abreakpoint, the corresponding breakpoints of all of said loading curvesoccurring at corresponding values of said total controlled-generationrequirements of said area, comprising means for generating a pluralityof signals each coresponding respectively in magnitude with desiredvalues of generation of each station-aft corresponding breakpoints,means for generating a signal reprsentative of saidcontrolled-generation requirementsof'the area, and computing meansjointly responsive to said signals for producing outputs to meet saidtotal controlled-generation requirements of said area and respectivelyrepresentative of desired generation of each said station in accordancewith said individual straightline segments determined by said adjacentbreakpoints.

`10. A generation controlv system 'for an interconnected generatinglarea -rnade up of a plurality of generating stations each Shaving atleast one generator, each olf said generating stations' having a loadingcurve representing the desired generation of the station in terms of thetotal controlled-generation requirements of the area and approximated bya plurality of straight-line segments of varying ldegrees of slope, eachsaid segment joining an adjacent segment at' a breakpoint, thecorresponding breakpoints of lall of said loading curves occurring atcorresponding values ofV said total generation requirements of -l- YaiI2 said area, comprising means including aplrality of summing circuitshaving applied thereto signals representative respectively of stationgeneration 'at said -breakpo'ints'for producing a `plurality oflimit-signals each in magnitude proportional to the su-m ofrtheseveral-values `of generation -of said stations at sai-dcorresponding,breakpoints, means for producing an area-generationsignal, comparison means -in number corresponding with-the number ofsaid breakpoints for comparing said area-generation signal with each ofVsaid limit signals,tand means jointly responsive to the outputs of saidcomparison `means and to said area generation signal lfor producing apluralityof desiredgeneration output signals one for each said stationproportional in magnitude tothe desired generationot each station tomeet the 'area-generation requirement with each vgenerating stationloaded in accordance with .its straight-line segment between `adjacentybreakpoints `lietween which said `area-generation requirementlies.

11. A generation controlsysteni :for an interconnected generating areamade up of a plurality of :generating sta-Y tions veach having at lleastone generator, each of said generating stations having a loading curverepresenting the desired generation of the station in terms :of thetotal controlled-generation requirements of the karea `andapproximatedby a plurality off straight-line segments .of varying`degrees of` slope, each said segment joining anadjacent segment at abreakpoint, the corresponding breakpoints of all of said loading curvesoccurring at corresponding values of said` total generationrequirementsof said area, comprising means including a plurality ofsumming circuits having applied thereto signals representativerespectively of. station generation at said breakpoints for generatingaplu'rality` of limit-signals each in magnitude proportional to the sumof theseveral values-ott generation of said stations at saidcorresponding breakpoints, means for producing an area-generationsignal, comparison means in number corresponding with the number ofsaid4 breakpoints for comparing said area-generation signal with each`of said limit signals, and means jointly responsive to the outputs ofsaid comparisonV means and to said karea-generation signal for producinga plurality of desired generation-output signals, one for each saidstation proportional in magnitude-to the desired generationl of eachstation to meet the area-generation requirement with each generatingstation loaded in accordance with its straight-line segment betweenadjacent breakpoints between Which said area-generation requirementlies, said jointly responsive means including an `amplifier havingnegative feed-back circuits respectively energized by signalsproportional in amplitudev to therespective generation` levels of saidstations vat said breakpoints between which said area-generationrequirement lies.

12. A generation control system for an interconnected generating areamade up of a pluralityl of generating stations each having at least onegenerator, each of said generating stations having a loading curverepresenting the desired generation ofthe station in terms of the totalcontrolled-generation requirements ,of the area and approximated by aplurality of straight-line segments `of varying degrees of slope, eachsaidscgment joiningan` adjacent segment at a |breakpoint, thecorresponding breakpoints of lall of said loading curves occurring atcorresponding values of said total generation requirements of Vsaidarea,

comprising means including a plurality of adjustable circuit Velementscorresponding in number with the number of said breakpoints andrespectively set to values proportional to the several levels of stationgenerationv at said breakpoints,`summing means, means including saidcircuit components for -applying to said summing means signalsproportional to adjacent breakpoints of loading curves of each of therespective generating stations plus the generation level ofeach'station'at the breakpoint oflesser value, amplifying -means havingan input circuit and an output cir-cuit, means connecting said outputcircuit to selected ones of said circuit components, an inverter hav- Yi3 ing its input connected to the output of said amplifier, saidinverter having an output circuit for supplying the remaining of saidcircuit components,- and means for applying to the input of said amplierthe output :from each of said summing means and an area-generation"signal.

13. The generation control systemof claim l2 in which there isinterposed between said selected circuit components and said remainingcircuit components circuit-reversing means -for interchanging theconnections from said amplifying means and from said inverter to saidcircuit components.

14. The generation control system of claim 13 in which saidcircuit-reversing means is operated from one to the other of saidpositions as said area-generation requirement changes in magnitude fromvalues lying between one adjacent pair of breakpoints to a value lyingbetween a second adjacent pair of breakpoints.

15. The generation control system of claim 14 in which saidcircuit-reversing means includes means including a plurality of summingcircuits having applied thereto signals representative respectively ofstation generation at said breakpoints for producing a plurality oflimit signals each in magnitude proportional to the sum of the severalvalues of generation of said stations at corresponding breakpoints,comparison means in number corresponding with the number of saidbreakpoints `for comparing at least one generation signal with each ofsaid limit signals, and means responsive to the outputs of saidcomparison means for operating said ycircuit-reversing means from one tothe -other of its positions each time the magnitude of said generationsignal changes above or below the magnitude of one of said limitsignals.

16. The `generation control system of claim l in which there areprovided relay means associated with the outputs o-f said comparisonmeans \for controlling the operation of said circuit-reversing means andin which there are associated with said circuit components a pluralityof circuitchanging ydevices operative under the control of said relaymeans for selectively connecting said circuit components to said summingmeans in response to the outputs from lsaidrcomparison means. Y

17. A system for dividing an input signal into a plural ity of outputsignals the sum of which is representative of said input signalcomprising means for establishing for each output signal lan upper-andlower limit of its range over which said output varies in linearrelation with said input, means for summing said established limits foreach said output for producing the corresponding upper and lower limitsof the range for said input signal, an output summing means, and meansfor applying to said output summing means for each said outputquantities representative of one limit oi the range for its respectiveoutput and representative of the amount said output should deviate fromsaid one limit in accordance with the amount said input deviates fromthe corresponding limit of said corresponding input range ifor producingfrom said output summing means said output signals.

18. In a generation control system Ifor a plurality of sources and inwhich each source has between a lower limit and an upper limit a linearrelationship between its change of generation and change in totalgeneration, comprising means for generating signals Yal and Yazrepresentative respectively of said lower and upper limits of saidsource generation, means for generating signals X1 and X2 respectivelyrepresentative of total generation corresponding with said lower andupper limits and respectively equal to means for generating a signal(-Em) representative of the total ydesired generation and lying betweensaid upper and lower limits for said total generation, and means forproducing an output signal of magnitude proportional to the signal Yazminus the product of the difference between the signal X2 minus thesignal (-Em) multiplied Y@ (Ya2+Yb2+Yc2 Yan Yai-l-Ybl-i-Yci YL1) Noreferences cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,071,693 January l, 1963 Frederick Beam Davis, 3rd

It is hereby certified that error appears in the above numbered patentrequiring Correction and that the said Letters Patent should read ascorrected below.

Column 9, line 70 for "Y' n read Yn Signed and sealed this 3rd day ofDecember -l963.

(sEAw Attest:

EDWIN L. REYNOLDS ERNEST W. SWIDER Attesting Officer AC i'lgCommissioner of Paienls UNITED STATES PATENT oEEICE CERTIFICATE OFCORRECTION Patent No. 3,071,693 January 1, 1963 Frederick Beam Davis,3rd

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 9 line TO, for "Y n read Y n (n+1) (HET)- u Signed and sealedthis 3rd day of December 1963,

(SEAL).

Attest:

EDWIN L. REYNOLDS ERNEST W. SWIDER Attesting Officer AC tingCommissioner of Paems

12. A GENERATION CONTROL SYSTEM FOR AN INTERCONNECTED GENERATING AREAMADE UP OF A PLURALITY OF GENERATING STATIONS EACH HAVING AT LEAST ONEGENERATOR, EACH OF SAID GENERATING STATIONS HAVING A LOADING CURVEREPRESENTING THE DESIRED GENERATION OF THE STATION IN TERMS OF THE TOTALCONTROLLED-GENERATION REQUIREMENTS OF THE AREA AND APPROXIMATED BY APLURALITY OF STRAIGHT-LINE SEGMENTS OF VARYING DEGREES OF SLOPE, EACHSAID SEGMENT JOINING AN ADJACENT SEGMENT AT A BREAKPOINT, THECORRESPONDING BREAKPOINTS OF ALL OF SAID LOADING CURVES OCCURRING ATCORRESPONDING VALUES OF SAID TOTAL GENERATION REQUIREMENTS OF SAID AREA,COMPRISING MEANS INCLUDING A PLURALITY OF ADJUSTABLE CIRCUIT ELEMENTSCORRESPONDING IN NUMBER WITH THE NUMBER OF SAID BREAKPOINTS ANDRESPECTIVELY SET TO VALUES PROPORTIONAL TO THE SEVERAL LEVELS OF STATIONGENERATION AT SAID BREAKPOINTS, SUMMING MEANS, MEANS INCLUDING SAIDCIRCUIT COMPONENTS FOR APPLYING TO SAID SUMMING MEANS SIGNALSPROPORTIONAL TO ADJACENT BREAKPOINTS OF LOADING CURVES OF EACH OF THERESPECTIVE GENERATING STATIONS PLUS THE GENERATION LEVEL OF EACH STATIONAT THE BREAKPOINT OF LESSER VALUE, AMPLIFYING MEANS HAVING AN INPUTCIRCUIT AND AN OUTPUT CIRCUIT, MEANS CONNECTING SAID OUTPUT CIRCUIT TOSELECTED ONES OF SAID CIRCUIT COMPONENTS, AN INVERTER HAVING ITS INPUTCONNECTED TO THE OUTPUT OF SAID AMPLIFIER, SAID INVERTER HAVING ANOUTPUT CIRCUIT FOR SUPPLYING THE REMAINING OF SAID CIRCUIT COMPONENTS,AND MEANS FOR APPLYING TO THE INPUT OF SAID AMPLIFIER THE OUTPUT FROMEACH OF SAID SUMMING MEANS AND AN AREA-GENERATION SIGNAL.